Cold therapy is an established practice used in the medical profession to treat certain limb injuries, such as, for example, sprained or strained arm or leg muscles, or injuries to joints. Generally, these types of injuries should be chilled to slow blood flow, which reduces swelling, pain, and further damage. A typical course of cold therapy treatment is to apply ice for a specified period to the injured region of the limb. Alternatively, a pack or bag containing a chemical agent that reacts (endothermically) to produce cold may be applied to the injured region.
Heat therapy may be used, in other circumstances, to warm up or limber muscles by increasing blood flow. For example, athletes may apply heat with a hot water bag for a specified period to thighs or calf muscles prior to an event. Alternatively, a pack or bag containing a chemical agent that reacts (exothermically) to produce heat may be applied to the region of interest.
A number of devices that use endothermic or exothermic reactions for cooling or heating body parts are known. For example, U.S. Pat. No. 4,986,076 to Kirk et al. and U.S. Pat. No. 2,898,744 to Robbins both disclose a flexible, plastic cooling bag sealed along its edges. The cooling bag is separated by a frangible barrier into two portions: a freezing chemical mixture (salt) portion and a liquid (water) portion. A cooling reaction is activated by squeezing or applying pressure to the bag, which ruptures the frangible barrier and thus allows the salt and liquid portions to mix. The resulting chemical mixture causes an endothermic reaction, which produces a cooling effect. The cooled bag is applied to a body part. However, once the chemical reaction is exhausted, the chemical mixture cannot be reactivated, and the cooling bag is thus not reusable. Moreover, separate bags are used for cooling and heating.
A reusable hot or cold pack is disclosed in U.S. Pat. No. 4,462,224 to Dunshee et al. A flexible pack, made from a polyester film material, is separated into three compartments. The adjacent compartments are separated by predictably rupturable seams. Two adjacent compartments contain either endothermic or exothermic reactant components. For example, one of those adjacent compartments contains a solvent composed primarily of water. The second compartment contains a water soluble, exothermic or endothermic solute. The third compartment, which is adjacent to the second compartment, contains a gelling agent. The endothermic or exothermic reaction is activated by pulling apart or jerking at the sides of the pack to rupture the seam between the first two compartments. After the chemical reaction is exhausted, the seam between the second and third compartments is ruptured. The gelling agent thus mixes with the already combined contents of the other compartments. The resulting gelled material can then be cooled in a refrigerator, and as such, the pack is reusable. However, the use of a gelled material requires access to a refrigerator to create the cooling effect, which is a very inconvenient process.
Accordingly, a need has arisen for a hot or cold chemical therapy device that is reusable but still convenient to use. A need also exists for a single, reusable device that can provide both heat and cold chemical therapy.